Are we living in an age of giant quakes?

Apr 08, 2011 By Becky Ham

Searching for patterns in the occurrence of large magnitude earthquakes after a succession of large tremors -- surpassed by the recent magnitude-9.0 quake in Japan -- has researchers wondering if the amount of big quakes is on the rise.

The devastating 2004 Indonesian tsunami, with its death toll of as many as 250,000 people, was caused by the first magnitude-9.0 earthquake since 1967. A succession of smaller but still destructive tremors in Haiti, Chile, and New Zealand -- surpassed by this year's magnitude-9.0 quake in Japan -- has some researchers wondering whether the number of large earthquakes is on the rise.

An earthquake represents the abrupt release of seismic strain that has built up over the years as plates of the Earth's crust slowly grind and catch against each other. Giant earthquakes live up to their fearsome name. The biggest ever recorded was the magnitude-9.5 Chile earthquake of 1960. It accounts for about a quarter of the total seismic strain released worldwide since 1900. In just three minutes, the recent quake in Japan unleashed one-twentieth of that global total according to geophysicist Richard Aster at the New Mexico Institute of Mining and Technology in Socorro.

The Indonesian quake "reinvigorated interest in these giants," said Aster, who is also president of the Seismological Society of America. The Chile and Japan earthquakes -- along with a magnitude-9.2 quake in Alaska in 1964 -- also triggered catastrophic tsunamis.

After a lull in large quakes in the 1980s and 1990s, we may now be in the middle of a new age of large earthquakes, Aster added.

Records from the past century reveal some periods that have seen an unusual number of giant earthquakes, defined as those with magnitude 8.0 or higher. For example, global seismic data show a dramatic spike in the rate of large earthquakes from 1950-67. But there have also been quiet periods with fewer large quakes. And with only 100 years worth of records to consult, researchers aren't sure what these patterns of large quakes might mean -- or whether they mean anything at all.

Tsunami damage along the waterfront of Kodiak, Alaska, after the 1964 magnitude-9.2 quake. Credit: USGS

Even if clusters of giant earthquakes are a real phenomenon, Aster noted, researchers don't have any good ideas on how one big quake can trigger another big one in a different part of the world.

Earthquakes are well known to generate smaller aftershocks, including some at great distance. The Japan quake spawned small tremors as far away as Nebraska.

But Andrew Michael, a geophysicist at the U.S. Geological Survey in Menlo Park, Calif., has studied the patterns in large earthquake occurrences that remain once aftershocks are removed from the picture. "Overall, the pattern is random," he said. Apparent clusters of large quakes can be explained simply as statistical flukes.

"Random doesn't mean evenly spaced out," Michael added. That's why quakes can seem to bunch together in the historical record. He cautioned that such clusters may not mean anything for predicting future earthquakes, or for explaining how a cluster of quakes might occur.

He compared the pattern to a baseball player's hitting slump. "It could mean that he needs to change something in his game. Or it could just be a random streak," Michael said.

Further evidence against the significance of apparent clustering came in a recent study by Don Parsons of the U.S. Geological Survey in Menlo Park and Aaron Velasco of the University of Texas at El Paso, published in Nature Geosciences. They found that large earthquakes do not generate other large quakes on a global scale.

Aster acknowledged that the rarity of large earthquakes means that questions about possible connections between them are difficult to answer. "We see magnitude-7 earthquakes only 15 or so times a year and magnitude-9 earthquakes only a few times a century," he said.

Michael said that until researchers know more about why the rate of large earthquakes varies over time "we shouldn't be worrying less, but there's no need for panic either."

The recent spate of giant earthquakes may not signal more to come, but Aster said that "it's undeniable that we're becoming more and more vulnerable to the effects of earthquakes in general."

Aster added that many rapidly growing cities around the world aren't prepared for a large quake, while at the same time coastal communities are expanding into tsunami-prone areas. "We just have more people in precarious places," he said.

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All of the recent earthquakes, in NZ and Japan have been on the same Plate - and the same subduction zone.Might that make it easier for quakes to affect each other?Surely the large movement of the north japan section will affect the probability of a south japan slip, the stresses and forces will have changed??If they don't affect each other, then WHY don't they - that is my question.

It depends on your definition of "giant". The seismologists' terms for large quakes are "strong" (magnitude 6.0 - 6.9), "major" (7.0 - 7.9), and "great" (8.0 and up). "Giant" is not one of the standard terms, so it has no standard meaning.

If we lay aside prejudice* we may discover that earthquakes are partially induced by continuously changing gravitational and magnetic interactions between the Earth, the Sun, the Moon and the planets.

*Scientists became so annoyed with astrologers for trying to predict the future of everything by the positions of these objects that they may have overlooked one obvious variable that may contribute to earthquakes.

Possibilities:1) Nibiru approaches2) Nemesis approaches3) Tevatron created a black hole awhile back which is swimming around in the core4) Mag pole shift5) Something else

The answer is #5, "Something else".

#1 and #2 are discountable, since there is no indisputable evidence even of the *existence* of Nibiru and Nemesis, much less of supposed gravitational effects thereof.

#3 is also a non-issue. First, Tevatron is very unlikely to be able to create a mini black hole; the LHC might, with a very small probability, be able to do it. Even if it did, the hole would evaporate via Hawking radiation very quickly, never being able to trouble the core (or anything else).

#4 is also ignorable. The magnetic poles do shift, but only very slowly. Field reversals are also slow, and their intervals are on the order of tens to hundreds of thousands of years.Most importantly, magnetic field changes do not affect tectonic structures.

The Bible foretold that great earthquakes in one place after another, accompanied by food shortages and diseases, signaled the end of the society, and world governments would topple like dominoes, we'd be useless to do anything to save ourselves and that we'd have only God to rely on at that point

The Bible foretold that great earthquakes in one place after another, accompanied by food shortages and diseases, signaled the end of the society, and world governments would topple like dominoes, we'd be useless to do anything to save ourselves and that we'd have only God to rely on at that point

As a layman, I have been studying this for many years, and as I see it, there are several areas that need more research by some more qualified than me.

As mentioned in the text, there may be a cycle of large earth quakes around the 60 year period, allthough accurate data for this is very limited. I do find it suprisingly coincidental that our own numerical system is based on the hexadecimal system. This cycle crops up in all sorts of places, even economics. It is also the approximate period for the alignment of Saturn and Jupiter.

We are constantly reminded that the the crust is still rebounding in places from the end of the last ice age.We have our selves just started to remove, at ever increasing speed the remainder of the ice. How we can expect to move such large volumes of water to different positions around the globe without some effect on techtonics is beyound me. I would expect the initial effects to be stronger, then over a long period the effects to tail off until - cont.

I am amazed at the apparantly coincidentl number of times that a strong 7+ magnitude earth quake is closely followed be a large quake on the opposite side of the globe. This occurs far more frequently than can be explaind by chance, allthough in every case we are assured by experts that ther was no conection. I think that in the case of large earthquakes the energy released is also transmited, and focused to the antipode. If there is a fault allready under strain in this region enough energy is transfered to trigger that fault to slip. In some extreme cases it can be like watching ping pong.

Anyway call me a crack pot if you like, and will keep watching the experts change there minds.

Tesla bosted that he could split the globe in half at the push of a button. The military released much radiation in the atmosphere to test the bomb before they went undeground. What's a few hundred thousand lives of collateral damage compared to the knowledge gained in testing such a device for future use?

When you see a new mountain range, 1000 meters high, appear, jutting out of the earth, where prior was only a grassy plain, then you will have experienced a giant quake.

I was under the impression that the kind of changes you are talking about don't generally happen at once. Where are you getting this scenario, is there real data for the description of this event or this an opinion?

I would rate 9.0 as a giant quake anywhere. Someone mentioned it isn't in the lexicon of descriptions that would allow even more freedom to throw the word around casually. So what would come after major quake as a description?

What? Nobody's mentioned Global Climate Change as the Obvious Cause yet? It's taking the blame for everything else that goes wrong these days, it seems ... why not this? (And probably for the absence of atmosphere on Mercury too, while we're at it!)

"We are constantly reminded that the the crust is still rebounding in places from the end of the last ice age.We have our selves just started to remove, at ever increasing speed the remainder of the ice. How we can expect to move such large volumes of water to different positions around the globe without some effect on techtonics is beyound me."

Tesla bosted that he could split the globe in half at the push of a button. The military released much radiation in the atmosphere to test the bomb before they went undeground. What's a few hundred thousand lives of collateral damage compared to the knowledge gained in testing such a device for future use?

The entire field of earthquake science seems pretty shaky to me. With that out of the way, tectonic plates are not separate entities floating in space somewhere but are all part of one system. The entire planet is that one system. What happens one place is connected in some manner to every other place on the planet. We still don't understand all the connections and ramifications but to think that any earthquake is an isolated event is to ignore the dynamics of our planet.

lets say the pressure was released on japan and the plate moved a few feet. then if you were to go in the direction that the plate was moving until you reached it's other edge you should see that a few feet of pressure was put on it.

lets say the pressure was released on japan and the plate moved a few feet. then if you were to go in the direction that the plate was moving until you reached it's other edge you should see that a few feet of pressure was put on it.

does this make sense or do i need to rewrite it?

There are a number of things moving in all different directions and at different speeds. Plates are also elastic like pizza. I think its a lot more complex than youre thinking.

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